**Core Concept**
Anorexia nervosa is a psychiatric disorder characterized by a distorted body image, excessive weight loss, and restrictive eating habits. It involves a complex interplay between psychological, neurological, and hormonal factors.

**Why the Correct Answer is Right**
The correct answer is related to the hypothalamic-pituitary-adrenal (HPA) axis dysregulation, which plays a crucial role in the pathophysiology of anorexia nervosa. The HPA axis is responsible for regulating stress response, appetite, and metabolism. In anorexia nervosa, chronic stress and restrictive eating lead to alterations in the HPA axis, resulting in decreased leptin levels, increased cortisol levels, and changes in appetite regulation.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because while there is some overlap between anorexia nervosa and obsessive-compulsive disorder (OCD), they are distinct psychiatric conditions with different underlying pathophysiology.
* **Option B:** This option is incorrect because while there is an association between anorexia nervosa and depression, it is not the primary characteristic of the disorder.
* **Option C:** This option is incorrect because while there is some overlap between anorexia nervosa and bulimia nervosa, they are distinct eating disorders with different underlying pathophysiology.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize that anorexia nervosa is a treatable condition, but early intervention is crucial. A comprehensive treatment plan should involve a multidisciplinary team, including a psychiatrist, psychologist, and a registered dietitian, to address the psychological, nutritional, and metabolic aspects of the disorder.

**Correct Answer: D.**